The present invention relates to a scroll fluid machine such as a scroll compressor, a scroll vacuum pump, a scroll expander or a scroll blower.
Such a scroll fluid machine comprises an orbiting scroll having an orbiting end plate and supported to turn on an eccentric shaft portion of a drive shaft via a bearing, and a stationary scroll having a stationary end plate. An orbiting wrap of the orbiting end plate engages with a stationary wrap of the stationary end plate to form a sealed chamber between the orbiting and stationary wraps. The scroll fluid machine has a self-rotation preventing mechanism for preventing rotation of the orbiting scroll.
By the eccentric shaft portion of the drive shaft and the self-rotation preventing mechanism, the orbiting scroll is eccentrically revolved. Depending on a revolving direction, the volume in the sealed chamber gradually decreases toward a center or increase away from the center, thereby compressing fluid sucked from the outer circumference toward the center or depressurizing fluid sucked from the center to discharge it through the outer circumference.
A housing of the scroll fluid machine is generally manufactured by die casting of Al alloy. During operation, a support portion for a ball bearing thermally expands to decrease holding force of the support portion, so that the ball bearing is likely to rotate in the support portion.
To prevent it, a cast iron reinforcement ring is cast into the support portion to restrain thermal expansion of the support portion and to increase strength thereof. However, the whole housing is made by die casting of Al alloy to limit restraint of thermal expansion of the support portion and not to achieve it sufficiently.
Furthermore, the reinforcement ring separately made of different material must be cast surely and firmly during die casting of Al alloy to obtain suitable product, which requires excellent technique and the increased number of steps to increase a total cost.